1. Field of the Invention
This invention relates to an air filter with a clog-detecting device.
2. Description of the Prior Art
A conventional air filter having function of indicating clogged conditions, as shown in FIGS. 1 and 2, which is disclosed in a R.O.C. patent NO. 520767 and a U.S. Pat. No. 6,723,159, includes an indicating device 22 assembled between the wind outlet 11 of a housing 1 and the exhaust orifice 21 of a windmill. The indicating device 22 is provided with a basic frame 221 pivotally connected with a pivot 222 having its outer end pivotally inserted out of the housing 1 and combined with an indicting needle 223, which can be turned together with the pivot 222 to move between a first location 12 and a second location 13 on the surface of the housing 1.The pivot 222 is secured with a wind-blocking sheet 224. Thus, when the filter unit of the air filter is in a normal condition without being clogged, air current exhausted from the exhaust orifice 21 to the wind outlet 11 is sufficient to drive the wind-blocking sheet 224 to turn and actuate the indicating needle 223 to move from the first location 12 to the second location 13. If the indicating needle 223 cannot be moved to the second location 13, it is indicated that the filter unit is clogged and has to be washed clean or replaced.
However, the convention air filter has the following drawbacks.
1. The indicating needle 223 is exposed to the outer surface of the housing 1 so it is likely to be bumped by external force to influence its accuracy.
2. Dust and impurities are easy to adhere to the joint location of the indicating needle 223 and the housing 1.
3. In the course of being transported, the housing 1 is liable to produce swinging and collision, causing friction and disengagement to the jointed portion of the indicating needle 223 and the pivot 222.
4. The conventional air filter is mostly installed at a high ceiling so it is hard to see and judge the accurate position indicated by the indicating needle 223.